drm/amd/display: enable_hpo_dp_link_output: Check link_res->hpo_dp_link_enc before...

drm/amd/display: enable_hpo_dp_link_output: Check link_res->hpo_dp_link_enc before using it

commit d925c04d974c657d10471c0c2dba3bc9c7d994ee upstream.

[WHAT & HOW]
Functions dp_enable_link_phy and dp_disable_link_phy can pass link_res
without initializing hpo_dp_link_enc and it is necessary to check for
null before dereferencing.

This fixes 1 FORWARD_NULL issue reported by Coverity.

Fixes: 0beca868cde8 ("drm/amd/display: Check link_res->hpo_dp_link_enc before using it")
Reviewed-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>